Photographic emulsion containing supersensitized pinacyanol



March 30, 1937. C, Ev K, MEI-:5 2,075,046

PHOTOGRAPHIC EMULSION CONTAINING SUPERSENSITIZED PINACYANOL Original Filed Nov. 4, 1932 lso Patented Mar. 30, i937 i TAFE' reim" FFECE PHOTGRAPHIC lE1Vl{`ULS01\T (CONTG SUPERSENSITHZED PINACYANOL Jersey Application November Li, 1932, Serial No. 641,177 Renewed February 9, 1935 l0 Claims.

This invention relates to sensitized photographic emulsions and more particularly relates to photographic emulsions such as those of the gelatino-silver-halide type containing a combination of sensitizers, one of which cooperates with the other to sensitize the emulsion to a much greater degree than is possible with that sensitizer, or either sensitizer alone, or even than would be evidenced by the sum total of the sensitization produced by the two separate sensitizers individually.

In other Words, I have found that the sensitivity contributed to photographic emulsions by certain sensitizers may be enhanced to a very considerable degree by adding to the basic sensitizer what I will term a supersensitizer, the latter contributing to the emulsion the sensitivity which is peculiar to itself as well as activating or inducing further sensitivity in what I will term the basic sensitizer. For example, a certain basic sensitizer may have a green speed of 50 I -I and D, but when there is added thereto a supersensitizer, which may not even sensitize to the green at all (but to some other portion of the spectrum) the green speed of the basic sensitizer will be increased far beyond its original green speed. Or, assuming the basic sensitizer to sensitize the emulsion to a green speed of 50 and the supersensitizer to separately sensitize the emulsion to a green speed of 5, the addition of the supersensitizer to the basic sensitizer will sensitize the emulsion to a green speed beyond the sum'total of the two separate green speeds, namely to a green speed, for instance of 80.

The combination of sensitizers and supersensitizers which are the subject of the instant invention have the peculiar property that, in order for the supersensitizer to increase the sensitivity of the basic sensitizer, the region of sensitivity of the supersensitizer must coincide at least in part with the region of sensitivity ofthe basic sensitizer. The unusual effects obtained by the combinations of sensitizers which constitute the lnstant invention result, therefore, from the unusual influence or relation which the supersensitizers have upon or to the respective basic sensitizers.

Accordingly, it is among the objects of my invention to provide a photographic emulsion which contains a basic sensitizer for the emulsion and which also contains a supersensitizer which contributes its own individual sensitization to the emulsion and also increases the sensitization caused by the basic sensitizer. It is a further object of my invention to provide certain combinations or mixtures of sensitizers in a photographic emulsion which will contribute to the emulsion a sensitivity (ability to respond to light) not heretofore obtainable with either of the individual sensitizers in the combination. Other objects will become apparent to those skilled in the art upon a further perusal of this specification,

I have found, for instance, that the sensitivity which pinacyanol contributes to a gelatino-silver-halide emulsion will be markedly increased if there is present in the photographic emulsion along with each part of the pinacyanol, from approximately lth part, or even less, to approximately one part, or even more, of certain styryl compounds as a supersensitizer. ersensitizing effect upon the sensitizing properties of pinacyanol to be general with or representative of certain styryl compounds which themselves have the ability of separately sensitizing photographic emulsions to some degree.

Referring to the attached drawing, forming a part hereof, there is represented a hypothetical wedge spectrogram illustrating my invention. The curve A shows the approximate sensitivity conferred upon a gelatino-silver-halide emulsion by pinacyanol as a basic sensitizer. The curve B illustrates diagrammatically the sensitivity separately conferred upon the same gelatino-silver-halide emulsion by a styryl compound, such as 4 methyl 2 (p. diethylamino styryl) thiazole ethiodide. The curve C, however, illustrates the sensitivity of the same photographie emulsion containing a small percentage of a solution in which is dissolved approximately equal parts of pinacyanol and the same styryl compound. From this it will be apparent that the combination or mixture of these sensitizers contributes to the photographic emulsion a sensitivity far beyond that which it is possible to obtain even from the sum total of the sensitization resulting from the individual sensitizers.

More specifically my invention is accomplished by dissolving the sensitizing dyes in, for instance, methyl alcohol. The sensitizer and supersensitizer are added to the alcohol, for instance, in equal proportions, although I have found that less than an equal amount of the supersensitizer is normally suicient to confer upon the sensitizer an increased sensitivity. For example, while I may dissolve in the methyl alcohol solvent one part of pinacyanol, I may then add to the alcohol from ,16th part, or even less, of the styryl compound to one part, or even more, of

the styryl compound,'depending upon the effect` I iind this supf that is desired in the photographic emulsion. The exact ratio of the supersensitizer to the sensitizer is not particularly important, inasmuch as those skilled in the art can readily 5 determine by what ratio the greatest degree of sensitization of the basic sensitizer can be obtained.

This solution of the sensitizer and supersensitizer is then diluted with water and a volume as 100 milligrams, and preferably from about 10 to 30 milligrams of the sensitizers, is then added to 1000 cc. of a gelatino-silver-halide emulsion, such as is customarily employed in the art. Obviously, if the pinacyanol is greatly supersensitized by the styryl compound, less of the sensitizer combination will be necessary to obtain the desired degree of sensitization in the emulsion. The emulsion may then be coated upon a transparent support as is well known in the art, either glass, cellulose nitrate or acetate, or other cellulose derivative, base being satisfactory as the support.

As further illustrating my invention, I have tabulated hereinafter typical examples of styryl compounds which themselves have the power of sensitlzing a photographic emulsion and also have the ability of supersensitizing the sensitizing effect of the pinacyanol on the photographic emulsion. Styryl compounds which are characteristic of those which I may employ as supersensitizers for pinacyanol are as follows: 4-methyl 2 (p. diethylamino) styryl thiazole ethiodide s 4-methyl 2 (p. dimethylamino) styryl thiazole ethiodide 4-phenyl 2 (p. dimethylamino) styryl thiazole ethiodide 2 (p. dimethylamino) styryl thiazole ethiodide 2 (p. dimethylamino) styryl thiazoline ethiodide pinaiiavol \N erben-@Merisi CzHs I These illustrate a class of styryl compounds 55 which I have found will act as supersensitizers for pinacyanol and which class may be dened as dialkylamino styryls which contain a simple heterocyclic nitrogen containing nucleus or ring which latter may be substituted, if desired, so long as such substitution does not destroy the power of the styryl to separately sensitize a photographic emulsion; alkyl and aryl groups are suitable substituents. I regard a fused-on benzene ring as being without the foregoing dei-lnition as for instance in the case of a quinoline or benzothiazole nucleus.

Pinacyanol is, of course, well known in the art as a sensitizer, having the formula- 01H5 C1B/s \I 75 The basic structure and source of the supercontaining from a few milligrams to as much` sensitizers above named are well known to those skilled in the art, either being set forth in the published literature, or in available patents, so that the description of their methods of preparation is unnecessary.

In addition to the above combinations of sensitizers, I have also found that a large number of combinations of other sensitizers will produce analogous results. For instance, as described in my application Serial No. 641,178, of even date, the sulphur or selenium containing pseudo cyanides may be supersensitized by those styryl compounds which contain a nitrogen containing heterocyclic nucleus which may or may not have a benzene ring fused thereon. As described in my application Serial No. 641,179, of even date, the sulphur or selenium containing carbocyanines may be supersensitized by the 2:2 alkyl 8 alkyl 3:4:3'z4 dibenzothiocarbocyanine halides. 'I'he numerous examples set forth in those applications further illustrate the principles of my invention.

Other examples showing the broad application of my invention could be cited but the foregoing will be suicient to teach those skilled in the art, the manner in which my invention is carried out and the broad principle of supersensitizing basic sensitizers of numerous types with compounds which themselves have separate sensitizing properties and the regions of sensitivity of which coincide at least in part with the respective regions of sensitivity of the basic sensitizers.

Numerous variations to the above invention will doubtless occur to those skilled in the art and will be included in the scope of my invention as defined by the claims appended hereto, it being understood that the foregoing is merely illustrative of the manner of practicing my invention and the results to be obtained thereby.

What I claim as my invention and desire to be secured by Letters Patent of the United States is:

1. A gelatino-silver-halide emulsion containing two sensitizers for the emulsion, one of which is pinacyanol as a basic sensitizer and the other of which is, as a supersensitizer, a vdialkylamino styryl derivative of an alkyl quaternary salt of a simple nitrogen-containing heterocyclic base.

2. A gelatino-silver-halide emulsion containing two' sensitizers for the emulsion, one of which is pinacyanol as a basic sensitizer and the other of which is, as a supersensitizer, a dialkylamino styryl derivative of an alkyl quaternary salt of a simple nitrogen-containing heterocyclic base which may be substituted but which has no fusedon benzene nucleus.

3. A gelatino-silver-halide emulsion containing two sensitizers for the emulsion, one of which is pinacyanol and the other of which is a 2 (p. dialkylamino) styryl thiazole alkhalide.

4. A gelatino-silver-halide emulsion containing two sensitizers for the emulison, one of which is pinacyanol and the other of which is 2 (p. dimethylamino) styryl thiazole ethiodide.

5. A gelatino-silver-halide emulsion containing two sensitizers for the emulsion, one of which is pinacyanol and the other of which is a 4 alkyl 2 (p. dialkylamino) styryl thiazole alkhalide.

6. A gelatino-silver-halide emulsion containing two sensitizers for the emulsion, one of which is pinacyanol and the other of which is 4 methyl 2 (p. diethylamino) styryl thiazole ethiodide.

'7. A gelatino-silver-halide emulsion containing two sensitizers for the emulsion, one of which is pinacyanol and the other of which is 4 methyl 2 (p. dimethylamino) styryl thiazole ethiodide.

8. A geiatinolsilver-halide emulsion containing two sensitizers for the emulsion, one of which is pinacyanol and the other of which is 4 aryl 2 (p. diaikylamino) styryl thiazoie alkhalide.

9. A gelatino-silver-halide emulsion containing two sensitizers for the emulsion, one of which is pinacyanol and the other of which is 4 phenyl 2 (p. dimethylamino) styryl thiazole ethiodide.

10. A photographic element comprising a gela tino-silver-halide emulsion containing two sensitizers for the emulsion, one of which is pinacywno1 as av basic sensitizer and the other of which is,l as a supersensitizer, a. dialkyiamino styryl derivative of an alkyl quaternary salt of a, simple rnitragen-containing heterocyclic base.

CHARLES E. K. MEES. 

